Currently, a central processing unit (CPU) is forced to dissipate heat with an axial flow fan or a centrifugal fan. As shown in FIGS. 1 and 2, a CPU 11 is attached to a radiator 13 and an axial flow fan 12 is attached to the radiator 13. The axial flow fan 12 includes a fan blade section 121 for inducing air flows. Since the heat produced by the CPU 11 is not evenly distributed over the surface thereof, the CPU 11 has a central area having a higher temperature than the rest part thereof. However, the conventional axial flow fan 12 is usually mounted directly above the CPU 11 while no air flow is produced at the center of the axial flow fan 12. As a result, the axial flow fan 12 does not allow the CPU 11 to have good heat dissipating effect.
Referring to FIGS. 3 and 4, a radiator 23 is attached to a CPU 21 and a centrifugal fan 22 is provided in a recess 231 on the radiator 23. The centrifugal fan 22 includes a fan blade section 221 for inducing air flows. Since the heat produced by the CPU 21 is not distributed evenly over the surface of the CPU 21, the CPU 21 has a central area having a higher temperature than the rest part thereof. It can be seen in FIG. 4 that the centrifugal fan 22 is usually mounted in the recess 231 directly above the CPU 21 while the air flows induced by the centrifugal fan 22 only flow toward an outer periphery of the centrifugal fan 21. Hence, the centrifugal fan 22 does not allow the CPU 21 to have good heat dissipating effect.